Primary Stability of Dental Implants in Human Jawbones: Experiments & FE Analyses

Primary stability (PS) is a key factor for promoting osseointegration and long-term success of dental implants particularly for immediate loading protocols. Beyond the current assessments of PS, an accurate pre-operative evaluation of PS would contribute to the improvement of surgical planning and treatment outcome. This study used biomechanical testing and homogenized finite element (hFE) analysis to objectively measure PS in the laboratory, and digitally estimate PS from prior μCT reconstructions.

Thirty-five bone samples extracted from the jaws of two donors were examined. Twenty-two were finally evaluated for PS. After scanning of the samples with μCT, implants were inserted by two experienced surgeons, and various metrics such as μCT-based bone volume fraction (BV/TV), insertion torque (IT), and resonance frequency analysis (RFA) were assessed to determine PS. Mechanical tests were conducted to measure ultimate force (UFexp) as an objective indicator of PS while the hFE simulations were performed to estimate this same ultimate force (UFsim).

Higher correlation was found between UFsim and UFexp (R² = 0.85) than between BV/TV and UFexp (R² = 0.61), IT and UFexp (R² = 0.50), and RFA and UFexp (R² = 0.38). All variables demonstrated a statistically significant linear correlation with UFexp (p < 0.01).

UFsim turns out to be a more reliable and objective indicator of PS than IT and RFA. The hFE analysis requires prior μCT reconstructions and is currently limited by numerical convergence problems. Despite these limitations, pre-operative hFE analysis emerges as a promising tool with a higher accuracy for estimation of PS than state of care techniques.